The present application is directed to device package and method of making a device package, and more particularly to a microelectromechanical systems (MEMS) device package having a reservoir containing lubricant compounds for forming passivation layers on a MEMS device.
Many microelectromechanical systems (MEMS) include moving components that place unique demands on surface lubrication and passivation systems. For example, metal, oxidized metal or semi-metal surfaces can make repeated contact during operation of MEMS devices. This repeated contact can result in undesirable sticking and friction, known as stiction, between the contacting surfaces. Stiction may be caused by, for example, the capillary action of water vapor present on the contacting surfaces, van der Waals attraction, and intermetallic bonding of metals.
One known approach for addressing the stiction problem is the application of passivation coatings, which can reduce stiction and wear between the contacting surfaces. Known passivation coatings include monolayers of long-chain aliphatic halogenated polar compounds, such as perfluorodecanoic acid (PFDA). This acid is characterized by a chain having an —CF3 group at a first end, a —COOH group at the second end, and intermediate —CF2 groups. The —COOH group allows the PFDA molecule to attach to desired surfaces of the MEMS, while the low surface energy —CF3 and —CF2 groups effectively lower the surface energy of the contacting surfaces of the MEMS, thereby reducing the stiction problem.
However, over time in a MEMS device, the repeated contact of moving surfaces may wear away the passivation coatings and increase the tendency for the moving surfaces to stick, adhere, or otherwise resist separation. This lack of stability of the surface coatings formed from PFDA and other perfluorinated carboxylic acids add to the costs of manufacturing of the MEMS devices. In addition, while halogenated polar compounds, such as PFDA, provide low-energy surface coating and result in satisfactory device performance, there are materials compatibility and handling issues associated with these compounds. Accordingly, there is a need for improved passivation compounds and systems for overcoming the above described problems.